Food products containing texturized milk proteins

ABSTRACT

The present invention relates to a dietary fiber composition produced by a process involving extruding a milk containing product (e.g., milk, milk concentrate, whey, whey concentrate, whey protein isolate) through an extruder at about 50-about 400 rpm and at a temperature of about 50° to about 120° C. to produce the dietary fiber composition. The present invention also concerns a fiber enriched food product containing at least one food ingredient and the dietary fiber composition described herein. In addition, the present invention relates to a method of making a fiber enriched food product, involving adding the dietary fiber composition described herein to one or more food ingredients or adding one or more food ingredients to the dietary fiber composition described herein. Furthermore, the present invention concerns a method of increasing fiber in the diet of a mammal, involving feeding to the mammal the fiber enriched food product described herein.

BACKGROUND OF THE INVENTION

The present invention relates to a dietary fiber composition produced bya process involving extruding a milk containing product (e.g., milk,milk concentrate, whey, whey concentrate, whey protein isolate) throughan extruder at about 50-about 400 rpm and at a temperature of about 50°to about 120° C. to produce the dietary fiber composition. The presentinvention also concerns a fiber enriched food product containing atleast one food ingredient and the dietary fiber composition describedherein. In addition, the present invention relates to a method of makinga fiber enriched food product, involving adding the dietary fibercomposition described herein to one or more food ingredients or addingone or more food ingredients to the dietary fiber composition describedherein. Furthermore, the present invention concerns a method ofincreasing fiber in the diet of a mammal, involving feeding to themammal the fiber enriched food product described herein.

As the reports of the health and nutraceutical benefits of consumingdietary fibers continue to grow, research is focused on increasing theamount, content and quality of fibers in human diet. Consumers as wellas nutrition-focused professional organizations are demanding increasedamounts of fiber in processed foods. The results of recent surveys ofthe amount of fiber consumed by Americans reveal that most consume lessthan 50% of the estimated desirable daily fiber intake. Current averagefiber intake is estimated at about 12 g/day, but the American DieteticAssociation recommends 20-35 g/day (J. Am. Dietetic Assoc., 93:1446-1447 (1993)).

Foods rich in fiber help with the management of a host of conditions.Associated healthful benefits of increasing fiber consumption includereduced risk of some types of cancer (including breast cancer) andcoronary heart disease, regulation of blood glucose and insulin,lowering the concentration of blood lipids, reduced risk ofcardiovascular disease and controlling diabetes, alleviatingconstipation, hemorrhoids and diverticulitis (Wolk, A., et al., JAMA,281(21): 1998-2004 (1999); Kritchevsky, D., Cereal Foods World, 42(2):81-85 (1977)). Thus it is desirable and beneficial to increase theamount of fiber in most prepared foods.

The Food and Agricultural Organization/World Health Organization(FAO/WHO), 1995 Codex Alimentarius Commission defines dietary fiber as,“the edible plant or animal material not hydrolyzed by the endogenousenzymes of the human digestive tract as determined by the agreed uponmethod.” Typical fiber sources are plant-based and include grains,fruits and vegetables; other less-traditional food fibers includeChitosan, a fat-binding dietary fiber derived from shellfish, andpolymeric components such as cell-wall proteins and phenolic compoundssuch as tannin and cutin.

Traditionally, the food industry uses native (folded) whey proteins fortheir functional and nutritional properties in formulating differentfoods. Though new products incorporating whey proteins, such as sportsdrinks, are being developed, innovation in process and productdevelopment is still needed (Anon., American Dairy Products Institute,Bulletin No. 25, p. 17 (2000)). Fortifying snacks with whey proteinscould provide a particularly attractive outlet for surplus wheyproteins; however, this practice has been limited due to known adversetextural effects when the whey protein concentrate supplementation isgreater than 10% of the main starch component (Kim, C. H., and J. A.Maga, Lebensmittel-Wissenchaft und-Technologie, 20: 311-318 (1987)).

The present invention provides proteins (e.g., whey proteins) that aretotally texturized and are insoluble to enzymes and protein cleavingchemicals (e.g., urea). The new product is indigestible and cantherefore serve as a fiber source. The fiber-like product described inthis invention is from an animal source (e.g., milk), but its propertiesare physiologically similar to plant-source dietary fiber, thus servingas a bulking agent and being nondigestible to enzymes. Alternate use forthis product include use in biodegradable products and utilization iningredients that require low gelling temperatures.

SUMMARY OF THE INVENTION

The present invention relates to a dietary fiber composition produced bya process involving extruding a milk containing product (e.g., milk,milk concentrate, whey, whey concentrate, whey protein isolate) throughan extruder at about 50-about 400 rpm and at a temperature of about 50°to about 120° C. to produce the dietary fiber composition. The presentinvention also concerns a fiber enriched food product containing atleast one food ingredient and the dietary fiber composition describedherein. In addition, the present invention relates to a method of makinga fiber enriched food product, involving adding the dietary fibercomposition described herein to one or more food ingredients or addingone or more food ingredients to the dietary fiber composition describedherein. Furthermore, the present invention concerns a method ofincreasing fiber in the diet of a mammal, involving feeding to themammal the fiber enriched food product described herein.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows electron micrograms of whey protein isolates (WPI): (A)scanning microscopy was used to examine dry powder; (B) the non extrudedWPI Paste (40% moisture) was embedded, stained with uranyl acetate andsections examined by transmission electron microscopy; (C) extruded(100° C.) WPI (40% moisture) treated as in (B);

FIG. 2 shows SDS PAGE of extruded whey isolates: (A) with2-mercaptoethanol; (B) without 2-mercaptoethanol; the lanes are: 1=100°C.; 2=75° C.; 3=50° C.; 4=35° C.; 5=Native WPI; 6=laboratory whey;

FIG. 3 shows transmission electron micrographs of whey protein isolates(WPI) positively stained with uranyl acetate and lead citrate: (A)enlargement of texturized whey as in FIG. 1C; (B) enlargement of aselected protein-dense area of FIG. 1B; (C) Fast Fourier Transforms ofelectron density images of native WPI; and (D) Fast Fourier Transformsof electron density images of texturized WPI; and

FIG. 4 shows electron-density mapping corresponding to the FourierTransforms (A) for texturized and native WPI, and (B) inverse reciprocalspacing of electron-density images.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to a dietary fiber composition containingcompletely texturized proteins. The dietary fiber composition isproduced by a process wherein the proteins in a milk containing product(e.g., milk, milk concentrate, whey, whey concentrate, preferably wheyprotein isolate) are completely texturized. This process involvesprocessing the milk containing product through an extruder (e.g., twinscrew extruder) at low shear (generally about 50-about 400 rpm (e.g.,50-400 rpm), preferably about 50-about 300 rpm (e.g., 50-300 rpm), morepreferably about 50-about 200 rpm (e.g., 50-200 rpm), most preferablyabout 50-about 100 rpm (e.g., 50-100 rpm) at a temperature of about 50°to about 120° C. (e.g., 50° to 120° C., preferably about 90° to about120° C. (e.g., 90° to 120° C.), more preferably about 95° to about 120°C. (e.g., 95° to 120° C.), most preferably about 100° to about 110° C.(e.g., 100° to 110° C.). Low shear increases the residence time of themilk containing product in the extruder since residence time is afunction of the rpm of the extruder, the residence time can increasefrom 45 to 90 seconds. Pressures may range from about 500 to about 1500psi (e.g., 500-1500 psi, preferably about 800 to about 1200 psi (e.g.,800-1200 psi)) and torque may range from about 30 to about 70% (e.g.,30-70%, preferably about 45 to about 55% (e.g., 45-55%)). The processmay also utilize other proteins such as, for example, soy protein,vegetable protein, animal protein.

The present invention also concerns a fiber enriched food productcontaining at least one food ingredient and the dietary fibercomposition. The food ingredient may be any food ingredient. Forexample, the food ingredient may be the ingredients for cookies ormuffins such as flour. Furthermore, the food ingredient may beshelf-stable packaged pre-mixes for preparing food and beveragecompositions, usually requiring the addition of other ingredients (e.g.,eggs, shortening, water or milk) to be supplied and added by thepreparer. Additionally, the food ingredient may be a ready-to-cook mix(combined food ingredients that require additional cooking (e.g.,baking, flying, micro waving) to form a ready-to-eat food or beverageproduct). Generally, the fiber enriched food product may be any foodproduct such as a drink, yogurt, or pizza, or a bakery product such ascake, biscuit, pie crust, cookie, muffin, bread, cereal, doughnut,noodle, brownie, cracker or snack food. The amount of the dietary fibercomposition contained in the fiber enriched food product may be anyamount that does not adversely affect the food product (for example, thefiber enriched food product may contain about 1% to about 40% of thedietary fiber composition, preferably about 5% to about 30%, morepreferably about 5% to about 20%, most preferably about 10% to about15%).

The texturized proteins of the present invention can be added to bakedsweet wafers to offer another type of protein enrichment to cookies orsnack bars. It may also be possible to utilize the texturized proteinsof the present invention in meal extenders and meat alternatives,function as instant thickeners for beverage and dairy applications, andalso finding use as edible films and encapsulating agents. Thetexturized proteins of the present invention may also function as aninstant thickening product which can be used in place of starch andother hydrocolloids; potential applications include baby food, sportsdrink and dairy foods such as sour cream, yogurt and cottage cheese.

The possibilities for texturized proteins of the present inventionextend past the grocery aisle. The texturized proteins of the presentinvention may make oxygen, aroma and oil barrier films atlow-to-intermediate relative humidity; may provide mechanical propertiesand adequate functionality when used as coating or encapsulating agents,providing durability when applied directly on foods or as films whenseparating layers of heterogeneous foods, or films formed into pouchesfor food ingredients; and may also be used as encapsulating agents.

Additionally, the present invention also relates to a method of making afiber enriched food product involving adding the dietary fibercomposition to one or more food ingredients (or vice versa). Forexample, in making cookies or muffins, the dietary food composition canpartially substitute for flour or be added in addition to flour in thepreparation of cookies or muffins. If cooking (e.g., baking, flying,micro waving) is required, then normal cooking conditions are utilized.

Furthermore, the present invention concerns a method of increasing fiberin the diet of a mammal involving feeding to the mammal the fiberenriched food product described herein. Generally, the mammal is ahuman.

Unless defined otherwise, all technical and scientific terms used hereinhave the same meaning as commonly understood by one of ordinary skill inthe art to which the invention belongs. Although any methods andmaterials similar or equivalent to those described herein can be used inthe practice or testing of the present invention, the preferred methodsand materials are now described.

The following examples are intended only to further illustrate theinvention and are not intended to limit the scope of the invention asdefined by the claims.

EXAMPLES

Materials And Methods:

Whey protein concentrate (ALACEN 834) and lactalbumin (ALATAL 825) werepurchased from New Zealand Milk Products, Inc. (Santa Rosa, Calif.).Whey Protein Isolate (PROVON 190) was purchased from GlanbiaIngredients. The compositions were as follows: WPC80 (whey proteinconcentrate, 80% protein), moisture 2.8%, protein 83.6%, fat 0.8, ash3.3%, carbohydrate by difference; WLAC (whey lactalbumin), moisture5.5%, protein 89.9%, fat 3.8, ash 0.5%, carbohydrate by difference; WheyProtein Isolate (WPI), moisture 2.8%, protein 89.6%, fat 25, ash 3.3%,carbohydrate by difference.

A ZSK-30 twin screw extruder (Krupp Werner Pfleiderer Co., Ramsey, N.J.)with a smooth barrel was used. The extruder had nine zones, and theeffective cooking zones 6, 7, 8, and 9 were set to the same temperaturefor each test. To achieve different melt temperatures the cooking zoneswere set to the same barrel temperature of 35, 50, 75, or 100° C.respectively. Zones 1 to 3 were set to 35° C. and zones 4 and 5 were setto 75° C. Melt temperature was monitored behind the die. The die platewas fitted with two circular inserts of 3.18 mm diameter each. The screwelements were selected to provide low shear at 300 rpm; the screwprofile was described by Onwulata et al. (Onwulata, C. I., et al., J.Food Sci. Vol., 63(5): 814-818). Feed was conveyed into the extruderwith a series 6300 digital feeder, type T-35 twin screw volumetricfeeder (K-tron Corp., Pitman, N.J.). The feed screw speed was set at 600rpm, corresponding to a rate of 3.50 kg/h. Water was added into theextruder at the rate of 1.0 L/h with an electromagnetic dosing pump(Milton Roy, Acton, Mass.). Samples were collected after 25 min ofprocessing, freeze-dried overnight in a VirTis Freeze Mobile 12XLResearch Scale Freeze Dryer (Gardiner, N.Y.), and stored at 4.4° C.until analyzed. The experiments were performed in triplicate.

Analysis of variance was used to identify differences in physicalproperties at various processing conditions. Duncan's multiple rangetest was used for mean separation and correlation coefficients werecalculated. The Statistical Analysis System (SAS) package was used (SASInstitute Inc, Cary, N.C.) in all cases. Significance of differences wasdefined as P≦0.05.

Moisture was determined by the AOAC (Association of Official AnalyticalChemists) Official Method 925.10. Extrudate samples weighingapproximately 1.5 g were dried in a vacuum oven at 100° C. overnight(AOAC, 2000, Official Methods of Analysis, 14th ed., Association ofOfficial Analytical Chemists, Washington, DC).

Ash was determined by the AOAC Official Method 923.03. Ash wasdetermined for each sample using 3 g assayed in a Muffler furnace at550° C. for 16 h; percent ash was calculated.

Fat was determined using the AOAC Official Method 30-25. One gramextrudate sample was placed in an Erlenmeyer flask and 1 ml of sulfuricacid and 4 ml water was added to the flask. The samples were mixedgently and after 60 min were transferred to a 60 ml separatory funnelusing 25 ml of dichloromethane: methanol solution (1:1). Extrudatesamples were shaken and allowed to separate for 15 min. The bottom layerwas drained into a weighing pan and then evaporated, and the amount offat determined (American Association of Cereal Chemists, 1995, ApprovedMethods of the American Association of Cereal Chemists, 9th Edition.,The Association, St Paul, Minn.).

Protein was determined with 0.2 g extrudate analyzed with the LECOProtein Analyzer Model FP2000 (LECO Corporation, St. Joseph, Mich.).Percent protein was calculated with the nitrogen conversion factor 6.38for whey protein.

Gel strength was measured by Bloom determinations with a TA-XT2 TextureAnalyzer (Ju, Z. Y., and A. Kilara, J. Food Sci. 63(2):288-292 (1998)).A 12% WPI solution was made (3.204 g of ground freeze-dried sample mixedwith 26.7 ml deionized water and 3.3 ml 0.03 M CaCl₂), and allowed tosit for 15 min in a 50×70 mm cylindrical jar. The sample was heated to80° C. for 30 min in a water bath, cooled in an ice bath for 15 min andthen stored overnight at 4° C. The specimen was thawed at 25° C. in 50%relative humidity room. Gel strength was determined with a TA-XT2Texture Analyzer running a penetration test with a 30 mm analyticalprobe to a depth of 6 mm at the rate of 1 mm/sec. The weak gels wereeasily deformed with evidence of syneresis.

Protein insolubility was determined with 1.0 g ground freeze-driedextrudate sample mixed with 90 ml deionized water. The proteinsuspension was stirred at 125 rpm at pH 7.0 for 2 h. The suspension wascentrifuged for 20 min and the supernatant was freeze dried overnight.The LECO Protein Analyzer Model FP2000 (LECO Corporation, St. Joseph,Mich.) was used to analyze the solids from the supernatant for proteincontent. Protein insolubility (denaturation) was calculated (Kilara, A.,J. Dairy Sci., 67:2734-2744 (1984)) as: (% Total Protein−% SolubleProtein=% Insoluble (denatured)).

Foam volume and stability of extruded proteins were determined byheating 2.3 g samples mixed with 35 ml deionized water to 60° C. for 15min. The slurry was then whipped for 15 sec in Waring Lab MicronizerFPC70 (Waring Products Division, New Hartford, Conn.), then transferredto a 100 ml graduated cylinder where the foam volume was read initially,and then every 5 min for 1 h. Foam stability (foam capacity at specifictime) over the one hour period was calculated.

Protein Digestibility was determined with 10 ml extrudate sampledissolved in distilled water, the pH was adjusted to 8.0 with 0.1 N NaOHor HCl. One milliliter of freshly prepared enzyme stock solution (1.6mg/ml trypsin, 3.1 mg/ml chymotrypsin, and 1.3 mg/ml aminopeptidase) wasadded to the protein suspension at 37° C. The pH after 10 min wasrecorded with a portable pH meter (IQ Scientific Instruments, Inc. SanDiego, Calif.), and a Tris/HCl buffer containing 2.0% SDS (w/v) and 0.1%mercaptoethanol (v/v) was added to the protein solution which wasimmediately heated to 90° C. to terminate the enzymatic reaction.Samples were then analyzed by quantitative gel electrophoresis. The %protein digestibility was calculated by the following equation (Ju, Z.Y., and A. Kilara, J. Food Sci. 63(2):288-292 (1998)): %Digestibility=210.46 B 18.10(X); where X is the pH .

For SDS PAGE assay, samples were vortexed and dissolved in 20 mMTRIS/HCl, 5 mM EDTA, 2.5% SDS with and without 5.0% 2-mercaptoethanol atpH=8.0 then heated in boiling water for 2 min. Bromophenol blue is addedto about 0.1% concentration. The samples were at 2 mg/ml concentration.Phast gels (Amersham Pharmaica Biotech, Uppsala, Sweden) were runaccording to the procedures given by the manufacturer for SDS 20%homogeneous gels. The 6 lane (4 ul per lane) sample applicators wereused. Protein staining used the coomassie blue procedure given by themanufacturer (Farrell, H., E. D., et al., J. Dairy Sci., 81:2974-2984(1998)).

For fine structure, transmission electron microscopy (TEM) was done ofthin sections made from epoxyembedded samples. Millimeter-sized piecesof coarsely ground; freeze-dried segments of ribbons of the extrudateswere immersed in 2.5% glutaraldehyde in 0.1 M imidazole buffer solution(pH 6.8) and stored in sealed vials at 4° C. For embedding and thinsectioning, the segments were washed in imidazole buffer, immersed in 2%osmium tetroxide in 0.1M imidazole buffer for 2 h at room temperature,washed in distilled water, and gradually dehydrated in a series ofethanol solutions and propylene oxide for one hour. Samples were theninfiltrated with a 1:1 mixture of propylene oxide and epoxy resinmixture overnight and finally embedded in epoxy resin. Thin sectionswere cut and stained with 2% uranyl acetate, and lead citrate solutions.TEM was done in the bright field mode using a model CM12 electronmicroscope (FEI/Philips, Hillsboro, Oreg.). Average spacings of electrondensity, corresponding to fine structure in the extrudates, wereestimated from the intensity distribution in Fourier transforms,computed from digital images made from TEM photographic negatives,recorded at 45,000×. Negatives were digitized using a SprintScan 45 filmscanner (Polaroid Corp., Cambridge, Mass.) and square areas of 2.8megabyte images (512×512 pixels) were transformed after flattening,adjustment of brightness and contrast and one cycle of a low pass filterusing a 3 H 3 pixel kernel in Image Pro Plus software (MediaCybernetics, Silver Spring, Md.). Line profiles of the radialdistribution of intensity in the Fourier transforms were made, andreciprocal spacings were calculated based on the location of orders ofpeaks in transforms of a line grating with an equivalent spacing of 22nm.

For scanning electron microscopy (SEM), a layer of dry powder particleswas adsorbed onto conductive carbon adhesive tabs glued to aluminumspecimen stubs (Electron Microscopy Sciences, Ft. Washington, Pa.), andthe surface was coated with a thin layer of gold in a model Scancoat Sixsputter coater (BOC Edwards, Wilmington, Mass.). Images of the powderparticles were made with a model JSM 840A scanning electron microscope(JEOL USA, Peabody, Mass.) operating in the secondary electron imagingmode and integrated with a digital image workstation, model Imix1(Princeton Gamma-Tech, Princeton, N.J.).

Results And Discussion:

Extruding whey proteins at the preset temperature of 75° C. resulted invarying degrees of melt temperatures and texturization for the differentproducts (Table 1; % is percent of texturized proteins). Followingextrusion, whey protein concentrate (WPC80) was the least texturized,and whey lactalbumin (WLAC) and whey protein isolates (WPI) weresignificantly (p<0.05) more texturized. WPI demonstrated the greatesteffect, changing from 28 to 94.8% texturized. Therefore, furtherexperiments were conducted with WPI.

The effect of extrusion cooking on texturized proteins was examined byelectron microscopy. Changes in the microstructure of WPI and theultrastructure of the texturized proteins are presented in FIG. 1. Themicrostructure of the dry powders, examined by scanning electronmicroscopy, reveal particles ranging from 10 to 50 micrometers indiameter (A). Transmission electron microscopy (B) shows the release ofprotein at the edge of powder particles after brief exposure to watertypical of initial mixing in the extruder; irregular strings andgranules, corresponding to molecular aggregates, ranging from less than10 nm to over 200 nm can be seen (B). In contrast, the ultrastructure ofextruder-texturized insoluble whey protein shows a closely-packedarrangement of electron dense particles, typical of texturized proteinmatrix, ranging from approximately 2 to 6 nm in diameter (C).

With the addition of shear in the extruder, significant unfolding(texturization) occurred at 75° C. WPI extruded at preset temperaturesat or above 50° C. texturized significantly (p<0.05) with increasedpreset temperature. The pH of the suspended protein remained stable asextrusion temperature increased, but measurable nitrogen (protein)increased as shown in Table 2. Loss of protein nitrogen might beexpected as temperatures increased above 80° C., but we surprisinglyobserved no significant change in protein nitrogen content after drying.Though the amount of protein texturized increased, with increasingtemperature, texturization had minimal overall effect on proteindigestibility. So the surprising result is increased proteintexturization without a significant loss of digestibility due toextrusion below 100° C.

The WPI and variously heat treated samples were compared by SDS-PAGE(FIG. 2). SDS gel of the variously texturized WPI indicated minimalchange in solubility (FIG. 2). SDS gels were initially developed withoutreducing reagent so the protein disulfide bonds are intact. Theunreduced samples at 35° C. and 50° C. show somewhat diminished bandsfor the higher molecular weight whey proteins (B). However, at 50° C.and 70° C. samples were equivalent weight, and fainter than the nativewhey or whey proteins produced in the lab on the SDS gel (compare lanes1 and 2 with 6 in FIG. 2). In this respect, the SDS gels parallel thesolubility data in that increased temperature decreases solubility inSDS alone, indicating sulfhydryl-disulfide crosslinking. When thesamples were reduced thoroughly and all disulfide bonds cleaved, all theextruded whey samples at the different temperatures were similar to eachother and to the initial WPI (A). Thus, extruding whey even at thehighest temperatures surprisingly does not affect the overall proteinratios. The native and extruded whey still have the same amount of thedifferent proteins (FIG. 2) and their total nitrogen values were similar(Table 2).

Physical functional properties of extruded WPI such as gel strength,foam volume and stability were significantly affected at and above 75°C., and proportionally at lower preset temperatures. Greater than 30%moisture was needed to extrude the whey protein isolates, but the onlysignificant change in moisture of the extruded products occurred at 100°C. (Table 3). Partial texturization at temperatures between 35° and 50°C. significantly increased gel strength, but at 75° C. or highercomplete loss of gelling property resulted. Foam volume remained high upto 50° C., but decreased significantly (p<0.05) after 75° C. Foamstability followed the same pattern as volume, being very stable for anhour below 50° C. However, with the addition of shear from the extruder,we observed significant loss of volume and stability.

Texturized whey protein isolate looks quite different from thenon-texturized proteins at the ultrastructural level (FIG. 3). Assampled, texturized proteins (3A) (WPI extruded at 100° C.) are denselypacked with spacing of 2 to 6 nm, while non-texturized whey in the pasteare loosely packed with a large spacing 200 to 350 nm (3B). Thedifferences in fine structure of texturized and native whey protein areillustrated in FIGS. 3 and 4. In the “native” whey protein (40% slurry),the distribution of electron density surrounding the hydrating particlesin FIG. 1B is an open network with clear, electron-lucent spaces rangingfrom 15-40 nm and irregular structures of electron density of similardimensions. In contrast, the fine structure in segments where the wheyproteins are completely texturized is limited to close-packed finegranules around 3-8 nm in diameter (FIG. 3). The corresponding computedFourier transforms indicate that images of extrudate containing nativewhey proteins consist mainly of low spatial frequencies indicatingstructures with average spacings ranging from 15 to over 40 nm, whereasimages of extrudate containing texturized whey proteins have littleintensity at low spatial frequencies, but high intensity correspondingto high spatial frequencies, relating to electron density changesranging from about 3 nm to less than 10 nm (FIG. 4). The constraint ofextruding whey is keeping the temperature below the point where pyrosiswill occur as evidenced by relatively constant nitrogen content (Table2). We have seen evidence of fine structures with TEM images at 100° C.in whey isolates.

We have thus created structured networks in whey proteins using mildheat and shear, to create reversible texturized whey proteins. Byunderstanding on a molecular basis the effects of shear, ways ofcreating new functionality can be developed. This will enabledevelopment of extrusion parameters that permit controlled texturizationof whey proteins.

Extrusion processing texturized whey protein concentrates, wheylactalbumin (LAC) and whey protein isolate (WPI), but the greatestamount of texturizing occurred with WPI. Texturized whey protein isolateretained its native protein value, functionality, and digestibility whenextruded at 50° C. or below; changes in functionality occurred at 75 and100° C. Through careful selection of extrusion conditions, texturizedwhey proteins with unique functionality were produced. Texturizationincreased with temperature, but temperatures higher than 100° C. may beneeded to form texturized fibrous products from whey protein isolates.We show here that extrusion is an effective tool for texturizing wheyproteins to create texturized products.

All of the references cited herein are incorporated by reference intheir entirety. Also incorporated by reference in their entirety are thefollowing references: Aboagye, Y., and Stanley, D. W.,Can-Inst-Food-Sci-Technol-J., 20(3):148-153 (1987); Batterman-Azcona, S.J., and Hamaker, B. R., Cereal Chem., 75(2):217-221 (1998); Farrell, H.M., Jr., et al., J. Dairy Sci., 85(3):459-471 (2002); Hale, A. B., etal., J. Food Sci., 67(3):1267-1270 (2002); Harper, J. M., Extrusion ofFoods, Vol. I., 1981, CRC Press, Boca Rotan, Fla.; Harwalkar, V. R.,Michwissenchaft, 34(7):419-422 (1979); Hong, Y., and L. K. Creamer,Int'l. Dairy J., 12:345-359 (2002); Kim, C. H., and J. A. Maga,Lebensmittel-Wissenchaft und-Technologie, 20:311-318 (1987); Kester, J.J., and T. Richardson, J. Dairy Sci., 67(11):2757-2774(1983);Kollengode, A. N., et al., J. Food Sci., 61(3): 596-599, 603 (1996);Martinez-Serna, M. D., and Villota, R., 1992, Reactivity, functionality,and extrusion performance of native and chemically modified wheyproteins, pages 387-414 in Food Extrusion Science and Technology, J. L.Kokini, C. Ho, and M. V. Karwe, ed., Marcel Dekker, Inc. New York;Mohammed, Z. H., et al., J. Food Sci., 65(2):221-226 (2000); Kester, J.J., and T. Richardson, J. Dairy Sci., 67(11):2757-2774 (1983); Lin, S.,et al., J. Food Sci., 67(3):1066-1072 (2000); Phillips, L. G., et al.,J. Food Sci., 55(4):1116-1119 (1990); Singh, R. K., et al., J. FoodProcessing and Preservation, 15:285-302 (1991); Taylor, S. M. and Fryer,P. J., Food Hydrocoll., 8 (1):45-61 (1994); Walstra, P., T. J., et al.,1999, pages 189-199 in Dairy Technology: Principles of Milk Propertiesand Processes, P. Walstra, T. J. Geurts, A. Noomen, A. Jellema, and M.A. J. S. van Boekel, ed., Marcel Dekker, Inc., New York.

Thus, in view of the above, the present invention concerns (in part) thefollowing:

A dietary fiber composition produced by a process comprising (orconsisting essentially of or consisting of) extruding a milk containingproduct through an extruder at about 50-about 400 rpm and at atemperature of about 50° to about 120° C. to produce said dietary fibercomposition.

The above dietary fiber composition, wherein said rpm is about 50-about300 rpm.

The above dietary fiber composition, wherein said rpm is about 50-about200 rpm.

The above dietary fiber composition, wherein said rpm is about 50-about100 rpm.

The above dietary fiber composition, wherein said temperature is about90° to about 120° C.

The above dietary fiber composition, wherein said temperature is about95° to about 120° C.

The above dietary fiber composition, wherein said temperature is about100° to about 110° C.

The above dietary fiber composition, wherein said process involves apressure of about 500 to about 1500 psi.

The above dietary fiber composition, wherein said process involves apressure of about 800 to about 1200 psi.

The above dietary fiber composition, wherein said process involves atorque of about 30 to about 70%.

The above dietary fiber composition, wherein said process involves atorque of about 45 to about 55%.

The above dietary fiber composition, wherein said milk containingproduct is selected from the group consisting of milk, milk concentrate,whey, whey concentrate, whey protein isolate, and mixtures thereof.

The dietary fiber composition, wherein said milk containing product isselected from the group consisting of whey concentrate, whey proteinisolate, and mixtures thereof.

A fiber enriched food product comprising (or consisting essentially ofor consisting of) at least one food ingredient and the above dietaryfiber composition.

A method of making a fiber enriched food product, comprising (orconsisting essentially of or consisting of) adding the above dietaryfiber composition to one or more food ingredients or adding one or morefood ingredients to the above dietary fiber composition.

A method of increasing fiber in the diet of a mammal, comprising (orconsisting essentially of or consisting of) feeding to said mammal theabove fiber enriched food product.

Other embodiments of the invention will be apparent to those skilled inthe art from a consideration of this specification or practice of theinvention disclosed herein. It is intended that the specification andexamples be considered as exemplary only, with the true scope and spiritof the invention being indicated by the following claims. TABLE 1Extrusion melt temperatures of whey proteins. Pre-Extrusion Product MeltTemperature (° C.) (%) Post-Extrusion (%) WPC80 70 ± 2 40.9 59.9 WLAC 75± 1 68.7 94.4 WPI 74 ± 1 28.0 94.8WPC80: Whey Protein Concentrate, 80% protein.WLAC: Whey Lactalbumin.WPI: WheyProtein Isolate: Number reported is mean of three samples.

TABLE 2 Properties of whey protein isolate (WPI) as function ofextrusion temperature. Insoluble Digestibility Extrusion Temp. (° C.)*pH Protein** (%) (%) (%) 35 6.7 90.7 28.4 89.6 50 6.8 90.9 33.3 88.2 756.9 91.7 77.7 85.7 100  7.0 91.4 87.2 84.5 PSD 0.2 0.7 1.2 0.6WPI: Whey protein isolates.*Preset barrel temperature of zones 6, 7, 8, 9.PSD: Pooled Standard Deviation.**% Protein after drying. Properties of non extruded WPI: pH 6.8,Protein 88.9%, Insoluble (Denatured) 28.0%, and Digestibility 87.7%.

TABLE 3 Physical properties of whey protein isolate (WPI) as function ofextrusion temperature. Extrusion Temp. Moisture Gel strength Foam (°C.)* (%) (N) Foam volume (%) stability 35 42.5 114.9 298.1 29.8 50 40.9145.3 301.9 30.2 75 42.6 2.8 173.3 17.3 100  38.9 # 77.1 7.7 PSD 0.7 1.91.2 1.1WPI: Whey protein isolates.*Preset barrel temperature of zones 6, 7, 8, 9.PSD: Pooled Standard Deviation. Properties of non-extruded WPI: Moisture1.94%, Gel Strength 52.3 (N), Foam volume 288%, and Foam stability28.7%.#: Value Not Reported.

1. A dietary fiber composition produced by a process comprisingextruding a milk containing product through an extruder at about50-about 400 rpm and at a temperature of about 50° to about 120° C. toproduce said dietary fiber composition.
 2. The dietary fiber compositionaccording to claim 1, wherein said rpm is about 50-about 300 rpm.
 3. Thedietary fiber composition according to claim 1, wherein said rpm isabout 50-about 200 rpm.
 4. The dietary fiber composition according toclaim 1, wherein said rpm is about 50-about 100 rpm.
 5. The dietaryfiber composition according to claim 1, wherein said temperature isabout 90° to about 120° C.
 6. The dietary fiber composition according toclaim 1, wherein said temperature is about 95° to about 120° C.
 7. Thedietary fiber composition according to claim 1, wherein said temperatureis about 100° to about 110° C.
 8. The dietary fiber compositionaccording to claim 1, wherein said process involves a pressure of about500 to about 1500 psi.
 9. The dietary fiber composition according toclaim 1, wherein said process involves a pressure of about 800 to about1200 psi.
 10. The dietary fiber composition according to claim 1,wherein said process involves a torque of about 30 to about 70%.
 11. Thedietary fiber composition according to claim 1, wherein said processinvolves a torque of about 45 to about 55%.
 12. The dietary fibercomposition according to claim 1, wherein said milk containing productis selected from the group consisting of milk, milk concentrate, whey,whey concentrate, whey protein isolate, and mixtures thereof.
 13. Thedietary fiber composition according to claim 1, wherein said milkcontaining product is selected from the group consisting of wheyconcentrate, whey protein isolate, and mixtures thereof.
 14. A fiberenriched food product comprising at least one food ingredient and thedietary fiber composition according to claim
 1. 15. A method of making afiber enriched food product, comprising adding the dietary fibercomposition according to claim 1 to one or more food ingredients oradding one or more food ingredients to the dietary fiber compositionaccording to claim
 1. 16. A method of increasing fiber in the diet of amammal, comprising feeding to said mammal the fiber enriched foodproduct according to claim 14.